You may enable the "Require Client Certificate to Access Web Interface" via the GUI through Settings > Security.   Under PKI and SSL settings, check "Require Client Certificate to Access Web Interface".

When you enable this feature, all web browsers that do not have a valid certificate from the Issuing Authority will be prevented from accessing the web interface. You will not be able to disable this feature through the WebUI unless you have a valid certificate.

 

At the CLI, you can disable Require Client Certificate to Access Web Interface by editing the file /etc/sysconfig/httpd and then restarting the service.

1. Edit httpd and set the export_SSL_ lines to "" (Two double quotes) and save the file.  After editing the file, the /etc/sysconfig/httpd with export SSL_ should look like:

export SSL_OPTIONS=""
export SSL_VERIFY_DEPTH=""
export SSL_VERIFY_REQUIRE=""
export SSLCA=""
export SSL_CRL_PATH=""

2. Restart the HTTP service. 

service httpd restart